This invention relates generally to gas cooking appliances, and, more particularly, to a gas shutoff valve assembly for a cooking appliance.
Gas fired stoves, ovens, and ranges typically include one or more gas heating elements coupled to a main gas line to the appliance and providing fuel to the heating elements, sometimes referred to as burners. In a domestic range, a gas line is connected to a distribution manifold within the appliance to direct gas to a plurality of surface burner elements on a cooktop or to baking elements within an oven cavity. Operation of the burners and cooking elements is usually accomplished with burner control knobs mounted on the front wall of the appliance in front of the cooktop. When a control knob is actuated, fuel is supplied to associated heating elements and an ignition module creates a spark to ignite the gas and produce a flame.
Unfortunately, the control knobs are often readily accessible to persons who are not able to safely operate the oven. For instance, an unsupervised child may turn the control knobs and light the burners or in some cases cause continuous flow of natural or propane gas that has not been lit, both of which are highly dangerous and undesirable conditions. Certain adults with mental conditions, including but not limited to dimensia, senility or Alzheimers disease, may also unwittingly or forgetfully activate the gas control knobs and light the burners or introduce highly combustible gas into the room.
To address these concerns, some gas fired cooking appliances include a valve to prevent gas flow to the burners when actuated (sometimes referred to as a lockout condition), and thus the appliance can be rendered inoperable as desired In some known appliances, however, mechanical controls for the lockout valve are rather easily accessible to appliance users. See, for example, U.S. Pat. No. 5,649,916. Consequently, the gas lockout valves themselves can be manipulated or relatively easily defeated by persons who are unable to use the appliance safely, resulting in potentially hazardous operating conditions.
One type of appliance includes a remotely actuated gas safety valve including a solenoid that is used to shutoff gas flow to the manifold which supplies gas to the multiple burners and heating units of the appliance. See, for example, U.S. Pat. No. 6,000,390. Solenoid operated valves, however, can be disadvantaged in several aspects.
For example, a normally closed fail safe solenoid valve must be continuously energized to supply gas to the heating elements whenever the control lockout feature is not activated, regardless of whether or not the appliance is actually used. Continuous energization of a solenoid is undesirable from both an energy consumption and appliance reliability perspective. Additionally, an AC solenoid produces an audible hum that may detract from the kitchen environment when the lockout feature is activated. While the hum of an AC solenoid may be eliminated by using a DC solenoid, a DC solenoid requires rectified AC power, which increases costs and introduces component reliability issues. Further, because the solenoid valve must be continuously energized to supply gas to the heating elements, the gas cooktop and gas heating elements become inoperable during a power outage. If the appliance is in use when power is lost, the denergized solenoid closes the valve and cuts off the gas fuel supply, and when power is restored the solenoid may become energized and open the valve, which will emit fuel into the room. While this problem may be overcome with electronic controls to prevent the solenoid from opening the valve when power is restored, the electronic controls introduce additional cost and complexity to the appliance control scheme. Still further, in existing systems it is sometimes difficult to determine whether the solenoid is activated or deactivated, and consequently whether the lockout system is properly functioning.